835 Denial Combination

CO-45+N1

CO

Contractual Obligation · Service-Line Level Adjustment

Contractual Adjustment

What This Combination Means

Note: An informational alert accompanies this denial. The payer reduced your charge to the contracted fee schedule or maximum allowable amount and is notifying you of your right to appeal. This combination appears contradictory since CO-45 typically represents a standard contractual write-off that would not be appealable, but the N1 remark explicitly states appeal rights are available. The payer may be treating this as a disputed fee schedule interpretation or legislated rate issue rather than a routine contractual adjustment.

Financial Responsibility

provider writeoff

Provider must write off the difference between the billed charge and the allowed amount per contractual obligation. Patient cannot be billed for this adjustment amount.

N/A

Appeal Success

60-90 days (appeal process)

Avg. Resolution

Hard

Difficulty

No

Appealable

Step-by-Step Resolution

Steps tailored specifically to this CO-45+N1 combination — not generic advice.

Not Appealable:Fee-schedule contractual adjustments under the CO group are write-offs per the provider agreement and are not appealable.
  1. 1

    Compare the paid amount against your contract's fee schedule for the specific service code and modifier combination

    Verify whether the payer applied the correct contracted rate, fee schedule tier, or legislated fee arrangement; look for rate table version mismatches or geographic modifier errors

  2. 2

    Document any fee schedule discrepancy or contracted rate interpretation issue with supporting contract language and rate schedules

    N1 indicates the payer is offering appeal rights on what appears to be a contractual adjustment, so identify the specific contract provision or legislated rate you believe was misapplied

  3. 3

    Submit a formal written appeal within the timeframe specified in your contract, attaching your contract fee schedule pages, rate effective dates, and explanation of the correct allowable

    Access the payer's appeal process guidelines via the URL provided in the ERA, as referenced in the N1 remark, and follow their specific submission requirements for fee schedule disputes

Specialty Context

How CO-45+N1 typically presents across different practice types.

Dental

Common for UCR (Usual, Customary, Reasonable) reductions or when billed fees exceed the plan's dental fee schedule; N1 may appear when provider disputes the fee schedule tier or percentile applied

Medical

Frequent with surgical procedures, imaging, and lab services where provider fee schedules differ significantly from payer allowables; appeal opportunity may exist for legislated rate disputes (e.g., Medicare fee schedule locality errors or workers' compensation rate misapplications)

Behavioral Health

Typical for psychotherapy and psychiatric services with wide fee variation; appeal rights may be relevant when payers incorrectly apply lower fee schedule tiers or fail to recognize credentialing-based rate differentials

Individual Code References

View the standalone definition for each code in this combination.

CARC 45RARC N1

Medicare Contractor Guidance for CARC 45

Noridian

Payment was made for this claim conditionally because an HHA episode of care has been filed for this patient.

How to Prevent CARC 45 Denials

  • ✓

    Ensure eligibility is verified in the Noridian Medicare Portal for Home Health Episode History (HHEH)

  • ✓

    Utilize the Consolidated Billing Tool on the Noridian Medicare website to inquire on items covered in a HHA episode of care, prior to providing

Noridian Medicare PortalConsolidated Billing ToolFee Schedule

Need to resolve this denial?

Get a complete resolution plan with appeal guidance for this exact combination in seconds.

Generate a free resolution plan & appeal letter →

Synthesized from official definitions — not from training data

Was this helpful?
← Back to Combo LookupBrowse All Codes →